The present invention relates to a production system or a rule based system for an expert system which employs a look-ahead inference type program and transforms existing implementations from one technology to another. In particular the present invention is suitable for automatic designing of a combinational logic circuit used in a large scale logic apparatus such as CMOS-LSI, LSI in a logic circuit design support system using a computer.
Technology for increasing the speed of a production system proposed so far lies on an extension of a rule compiler system which is based upon a discrimination net. With the algorithm of this type, the efficiency decreases drastically in a field of applications where conditions of production rules contain many variables, and the compiling time is extended, too. Moreover, the processing system itself becomes complex. In particular in a field which deals with circuit connection data such as of an equivalent conversion of logic circuit, the production rules inevitably contain increased number of variables. It is therefore necessary to realize a production system which is capable of operating at high speeds even in such a field of applications.
Examples of prior art disclosing a production system for an expert system are ; JP-A-61-109148 laid open on May 27, 1986, JP-A-60-24646 laid open on Feb. 7, 1985, JP-A-61-88371 laid open on May 6, 1986 which corresponds to U.S. Pat. No. 4,703,435 issued on Oct. 27, 1987, EP-A-0 199 304 laid open on Oct. 29, 1986 and Aart J. de Geus and William Cohen "A Rule-Based System for Optimizing Combinational Logic" (IEEE DESIGN & TEST, August 1985, PP 22-32).
In the aforementioned prior art, no attention has been given in regard to increasing the operation speed of the production system and, particularly, in regard to handling the substantially homogeneous data, such as logic circuit connection data. Therefore, the processing speed decreases when there are contained many variables in the respective condition parts of the production rules. Therefore, the production system spends extended periods of time for collating a tremendous number of production rules that are applicable, as the scale of the circuit to be converted and the number of rules increase.